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1.
J Evol Biol ; 18(1): 203-12, 2005 Jan.
Article in English | MEDLINE | ID: mdl-15669977

ABSTRACT

We investigated genetic diversity in West European populations of the fungal pathogen Microbotryum violaceum in sympatric, parapatric and allopatric populations of the host species Silene latifolia and S. dioica, using four polymorphic microsatellite loci. In allopatric host populations, the fungus was highly differentiated by host species, exhibiting high values of F(ST) and R(ST), and revealed clear and distinct host races. In sympatric and parapatric populations we found significant population differentiation as well, except for one sympatric population in which the two host species grew truly intermingled. The mean number of alleles per locus for isolates from each of the host species was significantly higher in sympatric/parapatric than in allopatric populations. This suggests that either gene flow between host races in sympatry, or in case of less neutral loci, selection in a more heterogeneous host environment can increase the level of genetic variation in each of the demes. The observed pattern of host-related genetic differentiation among these geographically spread populations suggest a long-term divergence between these host races. In sympatric host populations, both host races presumably come in secondary contact, and host-specific alleles are exchanged depending on the amount of fungal gene flow.


Subject(s)
Fungi/genetics , Genetic Variation , Genetics, Population , Silene/microbiology , Adaptation, Physiological , Europe , Host-Parasite Interactions , Selection, Genetic
2.
Heredity (Edinb) ; 93(4): 390-8, 2004 Oct.
Article in English | MEDLINE | ID: mdl-15241443

ABSTRACT

Apomictic plants often produce pollen that can function in crosses with related sexuals. Moreover, facultative apomicts can produce some sexual offspring. In dandelions, Taraxacum, a sexual-asexual cycle between diploid sexuals and triploid apomicts, has been described, based on experimental crosses and population genetic studies. Little is known about the actual hybridization processes in nature. We therefore studied the sexual-asexual cycle in a mixed dandelion population in the Netherlands. In this population, the frequencies of sexual diploids and triploids were 0.31 and 0.68, respectively. In addition, less than 1% tetraploids were detected. Diploids were strict sexuals, triploids were obligate apomicts, but tetraploids were most often only partly apomictic, lacking certain elements of apomixis. Tetraploid seed fertility in the field was significantly lower than that of apomictic triploids. Field-pollinated sexual diploids produced on average less than 2% polyploid offspring, implying that the effect of hybridization in the 2x-3x cycle in Taraxacum will be low. Until now, 2x-3x crosses were assumed to be the main pathway of new formation of triploid apomicts in the sexual-asexual cycle in Taraxacum. However, tetraploid pollen donors produced 28 times more triploid offspring in experimental crosses with diploid sexuals than triploid pollen donors. Rare tetraploids may therefore act as an important bridge in the formation of new triploid apomicts.


Subject(s)
Plants/metabolism , Reproduction, Asexual/physiology , Taraxacum/physiology , Hybridization, Genetic/physiology , Pollen/physiology , Polyploidy
3.
Heredity (Edinb) ; 93(1): 43-50, 2004 Jul.
Article in English | MEDLINE | ID: mdl-15138451

ABSTRACT

Male-sterility was found in diploid dandelions from two widely separated populations from France, and its inheritance was analysed by crossing a diploid male-sterile dandelion to diploid sexuals and triploid apomicts. Nuclear genetic variation, found in full-sib families, segregated for male-fertility, partial male-sterility, and full male-sterility, and also segregated for small-sized versus normally sized pollen. The crossing results are best explained by a cytoplasmic male-sterility factor in combination with two dominant restorer genes. Involvement of the cytoplasmic male-sterility factor was further investigated by chloroplast haplotyping. Male-sterility was exclusively associated with a rare chloroplast haplotype (designated 16b). This haplotype was found in seven male-sterile plants and one (apparently restored) male-fertile individual but does not occur in 110 co-existing male-fertile plants and not in several hundreds of individuals previously haplotyped. Apomicts with cytoplasmic male sterility were generated in some test crosses. This raises the question as to whether the male sterility found in natural dandelion apomicts, is of cytoplasmic or of nuclear genetic nature. As many breeding systems in Taraxacum are involved in shaping population structure, it will be difficult to predict the evolutionary consequences of nuclear-cytoplasmic male-sterility for this species complex.


Subject(s)
Diploidy , Taraxacum/genetics , Cell Nucleus/physiology , Chloroplasts/genetics , Crosses, Genetic , Cytoplasm/physiology , Fertility , Genetic Variation , Haplotypes , Phenotype , Pollen/genetics
4.
Heredity (Edinb) ; 93(2): 175-81, 2004 Aug.
Article in English | MEDLINE | ID: mdl-15138454

ABSTRACT

The mode of inheritance of the male sterility trait is crucial for understanding the evolutionary dynamics of the sexual system gynodioecy, which is the co-occurrence of female and hermaphrodite plants in natural populations. Both cytoplasmic (CMS) and nuclear (restorer) genes are known to be involved. Theoretical models usually assume a limited number of CMS genes with each a single restorer gene, while reality is more complex. In this study, it is shown that in the gynodioecious species Plantago coronopus two new CMS-restorer polymorphisms exist in addition to the two that were already known, which means four CMS-restorer systems at the species level. Furthermore, three CMS types were shown to co-occur within a single population. All new CMS types showed a multilocus system for male fertility restoration, in which both recessive and dominant restorer alleles occur. Our finding of more than two co-occurring CMS-restorer systems each with multiple restorer genes raises the question how this complex of male sterility systems is maintained in natural populations.


Subject(s)
Cytoplasm/genetics , Genes, Plant/genetics , Plantago/genetics , Polymorphism, Genetic , Crosses, Genetic , Ireland , Netherlands , Reproduction/genetics , Sex Factors , Sex Ratio
5.
Heredity (Edinb) ; 93(1): 22-33, 2004 Jul.
Article in English | MEDLINE | ID: mdl-15114368

ABSTRACT

The genetic basis of phenotypic plasticity of relative growth rate (RGR), its components and associated morphological traits was studied in relation to nutrient limitation. In all, 140 F(3) lines from a cross, made between two Hordeum spontaneum (wild barley) accessions sampled in Israel, were subjected to growth analysis under two nutrient levels. Quantitative trait loci (QTLs) were detected for RGR and three of its components, leaf area ratio (LAR), specific leaf area and leaf mass fraction (LMF). Indications for close linkage (potential pleiotropy) were found, for example, for LAR and LMF. An interesting case is on chromosome 6, at which QTLs for RGR and seed mass were detected in the same region. These QTLs had opposite additive effects, supporting earlier results that plants growing from lighter seeds had a higher RGR. Only two QTLs were significant under both nutrient conditions, suggesting large QTL x environment interactions for most traits. For 21 out of 26 QTLs, however, the additive genetic effect was of identical sign in both nutrient environments, but reached the significance threshold in only one of them. Nevertheless, some QTLs detected in one of the two environments had virtually no effect in the other, and QTLs for plasticity were detected for RGR, LAR and LMF, as well as for some morphological traits. QTLs with opposite effects under high and low nutrients were not found. Thus, at the genetic level, there was no evidence for a trade-off between faster growth at high versus low nutrient levels.


Subject(s)
Genes, Plant , Hordeum/genetics , Quantitative Trait Loci , Analysis of Variance , Chromosome Mapping , Crosses, Genetic , Hordeum/growth & development , Lod Score , Nutritional Physiological Phenomena , Phenotype
6.
J Evol Biol ; 17(1): 184-96, 2004 Jan.
Article in English | MEDLINE | ID: mdl-15000661

ABSTRACT

Across-species comparisons show that inherent variation in relative growth rate (RGR) and its underlying traits are correlated with habitat productivity. In this study, we test the hypothesis that growth rate-related traits confer differential selective effects in contrasting nutrient environments. We specifically test whether high RGR is targeted by selection in nutrient-rich environments whereas low values of traits that underlie RGR [specific leaf area (SLA), leaf mass fraction and leaf area ratio (LAR)] confer a direct fitness advantage in nutrient-poor environments, resulting in selection of low RGR as a correlated response. We measured RGR, its underlying component traits, and estimated fitness in a range of wild barley (Hordeum spontaneum) accessions grown under high and low nutrient conditions. Selection on component traits differed between the two environments, while total selection of RGR was not significant. Using multiple regression and path analysis to estimate direct fitness effects, a selective advantage of high LAR and SLA was demonstrated only under nutrient-rich conditions. While supporting the view that observed associations between habitat richness and some RGR-component traits reflect adaptation to differing nutrient regimes, our data suggest that direct selection targets component traits rather than RGR itself.


Subject(s)
Hordeum/growth & development , Nutritional Physiological Phenomena/physiology , Plant Leaves/physiology , Selection, Genetic , Analysis of Variance , Environment , Middle East , Regression Analysis
7.
Oecologia ; 137(4): 564-71, 2003 Dec.
Article in English | MEDLINE | ID: mdl-13680349

ABSTRACT

The Resource Availability Hypothesis (RAH) states that plants with a low Relative Growth Rate (RGR) and high levels of defence against herbivores or pathogens are favoured in habitats with low resource availability, whereas plants with a high potential RGR and low levels of defence are favoured in environments with high resource availability. High levels of defence are expected to result in lower reproduction and/or growth of the herbivores or pathogens. To test this hypothesis, four accessions of each of nine natural Hordeum spontaneum (wild barley) populations were grown in a climate chamber under two levels of nutrient supply. Susceptibility to Schizaphis graminum (greenbug) was quantified by placing a single adult greenbug on each plant and measuring its realised fecundity after 8 days. Data on potential RGR were available from a previous experiment. No support for the RAH was found. The correlation between potential RGR and greenbug reproduction was not significant, neither at the high nor at the low level of nutrient supply. Furthermore, on average plants grown under high and low nutrients did not differ in susceptibility. However, accessions-within-populations differed in the way susceptibility was affected by nutrient supply, and most accessions had a higher susceptibility under nutrient-poor conditions. It could be that these accessions differed in the spectrum of secondary metabolites they produced. Whatever the cause, the genetic variation for the reaction in susceptibility to nutrient supply suggests that selection could act in favour of more or less plasticity in plants without any apparent change in potential RGR.


Subject(s)
Aphids , Fertility , Hordeum/growth & development , Plants, Edible , Adaptation, Physiological , Animals , Climate , Feeding Behavior , Female , Male , Population Dynamics
8.
Heredity (Edinb) ; 78(Pt 1): 75-83, 1997 Jan.
Article in English | MEDLINE | ID: mdl-16397640

ABSTRACT

MtDNA restriction fragment polymorphisms were found between cytoplasmic male-sterility types P and R of Plantago lanceolata with the homologous probe pPl311 and maize mtDNA fragments derived from the regions of atp1, cox1 and cox2. No mtDNA differences were observed between male- sterile and restored plants with the same cytoplasmic type. The con-sistency of the polymorphisms was studied in 83 plants from 24 natural populations in the Netherlands. Within the R-cytoplasm no mtDNA polymorphisms were found, whereas seven variant mtDNA RFLP patterns were observed within the P-cytoplasm using pPl311. We also report on a putative new cytoplasmic male-sterility type, which showed a unique RFLP pattern supporting its distinct status.

9.
Genetics ; 147(3): 1317-28, 1997 Nov.
Article in English | MEDLINE | ID: mdl-9383073

ABSTRACT

Male fertility in Plantago lanceolata is controlled by the interaction of cytoplasmic and nuclear genes. Different cytoplasmic male sterility (CMS) types can be either male sterile or hermaphrodite, depending on the presence of nuclear restorer alleles. In three CMS types of P. lanceolata (CMSI, CMSIIa, and CMSIIb) the number of loci involved in male fertility restoration was determined. In each CMS type, male fertility was restored by multiple genes with either dominant or recessive action and capable either of restoring male fertility independently or in interaction with each other (epistasis). Restorer allele frequencies for CMSI, CMSIIa and CMSIIb were determined by crossing hermaphrodites with "standard" male steriles. Segregation of male steriles vs. non-male steriles was used to estimate overall restorer allele frequency. The frequency of restorer alleles was different for the CMS types: restorer alleles for CMSI were less frequent than for CMSIIa and CMSIIb. On the basis of the frequencies of male steriles and the CMS types an "expected" restorer allele frequency could be calculated. The correlation between estimated and expected restorer allele frequency was significant.


Subject(s)
Alleles , Genes, Plant , Plantago/genetics , Plants, Medicinal , Chromosome Mapping , Fertility/genetics , Gene Frequency , Nuclear Proteins/genetics
10.
Genetics ; 139(4): 1749-58, 1995 Apr.
Article in English | MEDLINE | ID: mdl-7789775

ABSTRACT

Inheritance of male sterility was studied in the gynodioecious species Plantago coronopus using five plants and their descendants from an area of approximately 50 m2 in each of six locations. The crosses were planned to test for cytoplasmic inheritance of male sterility. In four locations significant differences between reciprocal crosses were observed. The progenies of these reciprocal crosses were used in a crossing scheme designed to test whether these reciprocal differences were caused by different cytoplasmic types between the plants. In all four locations, the existence of at least two cytoplasmic types could be shown. Moreover, the results of the crosses between locations showed that the same two cytoplasmic types were present in all four locations. We therefore argue that there is only limited cytoplasmic variation in P. coronopus. In each cytoplasmic type a series of intermediate sex forms occurred. A marked difference in restoration level existed between the two cytoplasmic types. Plants with cytoplasmic type 2 hardly segregated male steriles, in contrast to plants with cytoplasmic type 1.


Subject(s)
Cytoplasm/genetics , Genetic Variation , Plantago/physiology , Plants, Medicinal , Crosses, Genetic , Genes, Plant , Plantago/genetics , Reproduction/genetics
11.
Genetics ; 139(4): 1759-75, 1995 Apr.
Article in English | MEDLINE | ID: mdl-7789776

ABSTRACT

Inheritance of male sterility was studied in the gynodioecious species Plantago coronopus using five plants and their descendants from an area of approximately 50 m2 from each of four locations. In each location, crosses between these five plants yielded the entire array of possible sex phenotypes. Both nuclear and cytoplasmic genes were involved. Emphasis is placed on the nuclear (restorer) genetics of two cytoplasmic types. For both types, multiple interacting nuclear genes were demonstrated. These genes carried either dominant or recessive restorer alleles. The exact number of genes involved could not be determined, because different genetic models could be proposed for each location and no common genetic solution could be given. At least five genes, three with dominant and two with recessive restorer allele action, were involved with both cytoplasmic types. Segregation patterns of partially male sterile plants suggested that they are due to incomplete dominance at restorer loci. Restorer genes interact in different ways. In most instances models with independent restorer gene action were sufficient to explain the crossing results. However, for one case we propose a model with epistatic restorer gene action. There was a consistent difference in the segregation of male sterility between plants from the two cytoplasmic types. Hermaphrodites of cytoplasmic type 2 hardly segregated male steriles, in contrast to plants with cytoplasmic type 1.


Subject(s)
Genetic Variation , Plantago/physiology , Plants, Medicinal , Alleles , Cell Nucleus/genetics , Genes, Plant , Phenotype , Plantago/genetics , Reproduction/genetics
12.
Eur J Biochem ; 221(2): 769-77, 1994 Apr 15.
Article in English | MEDLINE | ID: mdl-8174556

ABSTRACT

Mannose-binding lectins were purified from the leaves of three Orchidaceae species, namely Listera ovata (twayblade), Epipactis helleborine (broad-leaved helleborine) and Cymbidium hybrid, using affinity chromatography on Mannose - Sepharose-4B. Apparently, the Orchidaceae lectins are dimeric proteins composed of lectin subunits of 12-13 kDa. All of the isolated lectins exhibit exclusive specificity towards mannose. A cDNA library constructed from poly(A) rich RNA isolated from leaves of L. ovata was screened for cDNA clones encoding the lectin using colony hybridization. Since N-terminal sequence analysis of the twayblade lectin revealed some sequence similarity to the previously cloned mannose-binding lectin Hippeastrum hybrid (amaryllis) ovaries, the amaryllis lectin cDNA clone was used as a probe to screen the L. ovata library. Subsequently, the cDNA clone encoding the L. ovata lectin was used to screen the cDNA libraries from the taxonomically related orchid species Cymbidium hybrid and E. helleborine. Sequence analysis of the lectin cDNA clones from different Orchidaceae species revealed approximately 50% sequence similarity both at the nucleotide and amino acid level. The Orchidaceae lectins are apparently translated from mRNAs consisting of approximately 800 nucleotides. The primary translation products are preproproteins which are converted into the mature lectins following post-translational modifications. Southern blot analysis of genomic DNA has shown that the lectins are most probably encoded by a family of closely related genes which is in good agreement with the sequence heterogeneity found between different lectin cDNA clones of one species.


Subject(s)
Carrier Proteins/chemistry , Lectins/chemistry , Plants/chemistry , Agglutination Tests , Amino Acid Sequence , Base Sequence , Blotting, Northern , Blotting, Southern , Carrier Proteins/genetics , Carrier Proteins/metabolism , Chromatography, Ion Exchange , Cloning, Molecular , DNA, Complementary/chemistry , DNA, Complementary/genetics , Electrophoresis, Polyacrylamide Gel , Lectins/genetics , Lectins/metabolism , Mannose-Binding Lectins , Molecular Sequence Data , Plant Lectins , Plants/genetics , Sequence Homology, Amino Acid , Sequence Homology, Nucleic Acid , Software
13.
Eur J Biochem ; 217(1): 123-9, 1993 Oct 01.
Article in English | MEDLINE | ID: mdl-8223549

ABSTRACT

Lectin cDNA clones encoding the two mannose-binding lectins from ramsons (allium ursinum L.) bulbs, AUAI and AUAII (AUA, Allium ursinum agglutinin), were isolated and characterized. Sequence comparison of the different cDNA clones isolated revealed three types of lectin clones called LECAUAG0, LECAUAG1 and LECAUAG2, which besides the obvious differences in their sequences also differ from each other in the number of potential glycosylation sites within the C-terminal peptide of the lectin precursor. In vivo biosynthesis studies of the ramson lectins have shown that glycosylated lectin precursors occur in the organelle fraction of radioactively labeled ramson bulbs. Despite the similarities between the A. ursinum and the A. sativum (garlic) lectins at the protein level, molecular cloning of the two ramson lectins has shown that the lectin genes in A. ursinum are organized differently. Whereas in A. sativum the lectin polypeptides of the heterodimeric ASAI are encoded by one large precursor, those of the heterodimeric AUAI lectin are derived from two different precursors. These results are confirmed by Northern blot hybridization of A. ursinum RNA which, after hybridization with a labeled lectin cDNA, reveals only one band of 800 nucleotides in contrast to A. sativum RNA which yields two bands of 1400 and 800 nucleotides. Furthermore it is shown that the two mannose-binding lectins are differentially expressed.


Subject(s)
Allium/genetics , Lectins/genetics , Mannose/metabolism , Amino Acid Sequence , Base Sequence , Blotting, Northern , Chromatography, Gel , Cloning, Molecular , DNA, Complementary/chemistry , DNA, Complementary/isolation & purification , Electrophoresis, Polyacrylamide Gel , Glycosylation , Lectins/chemistry , Lectins/metabolism , Molecular Sequence Data , Plant Lectins , Sequence Homology, Amino Acid
14.
Oecologia ; 86(3): 359-367, 1991 May.
Article in English | MEDLINE | ID: mdl-28312921

ABSTRACT

The amount of genetic variation within a population is, among other things, related to population size. In small populations loss of genetic variation due to high levels of genetic drift and inbreeding may result in decline of individual fitness and increase the chance of population extinction. This chain of processes is known as genetic erosion. In this study we tested the genetic erosion hypothesis by investigating the relation between morphological variation and population size in two perennial, outbreeding plant species, Salvia pratensis and Scabiosa columbaria. To relate phenotypic variation to genetic variation the experiments were performed under common environmental conditions. For both species a positive correlation was observed between the amount of phenotypic variation and population size (Salvia r=0.915; Scabiosa r=0.703). Part of this variation is likely to have a genetic base, although maternal effects were present in the seedling and juvenile life stages. Differences between populations could in both species be attributed to parameters related to fitness, i.e. growth rate in Salvia and reproductive effort in Scabiosa. Discriminant functions reflecting these parameters did not however discriminate between large and small populations.Results are discussed in relation to the common environment approach and to electrophoretic results obtained earlier (Van Treuren et al. 1991).

15.
Theor Appl Genet ; 76(2): 190-6, 1988 Aug.
Article in English | MEDLINE | ID: mdl-24232105

ABSTRACT

Outcrossing rates were estimated in three populations of the gynodioecious species Plantago coronopus by means of electrophoresis of adult plants and their natural progenies. A multilocus estimation procedure was used. Heterogeneity among the pollen-pool allele frequencies did not exist either in space of in time. Differences between populations in mean outcrossing rates were large (range: 0.34-0.93), probably caused by differences in densities of flowering plants. In addition, there was considerable variability between individuals, which was at least partly caused by the presence of male sterility. Population density may, via its influence on outcrossing rates, be a factor influencing the maintenance of male sterile plants in the population. The level of outcrossing in hermaphrodites was not low enough to explain the maintenance of male steriles. Outcrossing rates in two populations, established via progeny analysis, were much lower than calculated with the fixation index, possibly indicating heterozygote advantage in these natural populations.

16.
Trop Geogr Med ; 37(3): S21-32, 1985 Sep.
Article in English | MEDLINE | ID: mdl-4084365

ABSTRACT

The purpose of the paper is to draw attention to the fact that drinking water supply and the provision of sanitation facilities form an indispensable element in disease prevention and primary health care programmes. The world situation regarding the availability of drinking water and sanitation facilities is dramatic, in that more than 1500 million people lact proper facilities; the implications in terms of health and cost are stupendous. It is therefore a fortunate development that the International Drinking Water and Sanitation Decade (1981-1990) is on its way to an appealing initiative. The paper discusses water and sanitation related diseases, and the established experience that water and sanitation programmes can only have a health impact if they are jointly developed, and if they are integrated with health education. Operational implications of such programmes as an element of primary health care are reviewed.


Subject(s)
Developing Countries , Public Health , Sanitation , Water Supply , Adolescent , Child , Child, Preschool , Disease Outbreaks , Health Education , Humans , Infant , Infant, Newborn , Parasitic Diseases/transmission
17.
Sci Total Environ ; 18: 307-15, 1981 Apr.
Article in English | MEDLINE | ID: mdl-7233170

ABSTRACT

Among the major water supply problems in developing countries are the lack of qualified manpower, inadequate management, and limited financial resources. Trained personnel is not only deficient in many of the water agencies, but also in ministries, health agencies, community organizations and labour categories of all kinds. Operation and maintenance, quality control and revenue collection leave much to be desired. The scarce resources are barely or not at all sufficient to scope with the day to day problems, let alone with investments for the future. These situations differ considerably from region to region. Several countries may have manpower available but lack finance. Others may have ample funds, but have a shortage of trained people. Many have neither of them. Management problems occur almost everywhere. Each of the countries has its own options and constraints for future developments. In many developing countries there is also a serious scarcity of water resources. In these countries the introduction of water reuse practices would be an obvious option. The policies and the choice of technologies however, should be seen in the light of these countries overriding problems.


Subject(s)
Developing Countries , Water Supply/standards , Technology
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